In all digital playback systems, a key component is the conversion of pixels represented in the YUV, or luminance-chrominance color space to a value in the RGB, or Red-Green-Blue color space. The YUV pixels are those that are typically provided via an external video device such as a video camera, video tape player, etc. Digital Video is often stored with some form of data compression; video decompression processors will most often output data in YuV format. The pixels represented in the RGB format are used to display images on a display device, such as a computer monitor, etc.
Efficiency is critical for the translation operation because it must be executed for each input video pixel; speed enhancements at this stage of operation can therefore provide a dramatic improvement on the performance of the overall video system.
One problem with providing efficient translation arises when considering the additional step of color adjustment. Raw pixel data may require color adjustment for display on the output device, since the raw input data and output display device may not always be compatible. It is a main objective to provide a pleasing output image; therefore, often the hue, saturation, or brightness of the image must be adjusted at some point prior to display.
However, adjustment causes an additional step that may accordingly reduce performance. One method of color adjustment, described in pending U.S. patent Ser. No. 07/961,558, filed Oct. 15, 1992 entitled "Imaging System with Image Adjustment System", by Ulichney et al. used a table for storing adjusted pixel values. Raw input pixel values were fed to the table, and the adjusted values were then fed for use to the video logic.
While the above system provided a means for color adjusting raw pixel values, it had some drawbacks. An extra table look-up had to be performed before any work could be done with the pixel value, thereby increasing the remaining time available for pixel operation. In addition, it provided an inflexible approach because it was limited simply to color adjustment based on certain input variables.